PHP singleton mode encapsulates MySQL classes

class MysqlConn { 
　　//Define a private static property to store the instantiated object 
    private static $dbcon; 
　　//Define a private static property for the connection to the database 
    private static $conn; 
　　//Define a private Deconstruction function to connect to the database 
    private function __construct() 
    { 
        self::$conn = mysqli_connect($host,$username,$password,$dbname) or die('Connection failed:'.mysqli_error().mysqli_errno()) ; 
    } 
　　//Define a private clone method 
    private function __clone() 
    { 
        // TODO: Implement __clone() method. 
    } 
　　//Public static method to return class instance 
    public static function getInstance(){ 
        if (!self ::$dbcon){ 
            self::$dbcon = new self(); 
        } 
        return self::$dbcon; 
    }
　　//You can define various functions of MySQL later 
    public function search($sql){ 
        $result = mysqli_query(self::$conn,$sql); 
        return mysqli_fetch_assoc($result); 
    } 
} 
//call method 
$conn = MysqlConn::getInstance(); 
$sql = "select * from `table_name`"; 
$rows = $conn->search($sql); 
echo '<pre>'; 
var_dump($rows);